feat(ios): allow for for per-image-request-headers (DylanVann#691)

* Bump the dependency of SDWebImage into 5.8+ because of the SDWebImageDownloaderRequestModifier convenient API usage
* Fix the implementation on iOS for per-image-request-header-setup. Should not use `SDWebImageDownloader` which manage the global shared headers. Use the context option of request modifier.
* Add the support for data:image URL for WebP images
* Alaways bypass invalid SSL certificate error, same behavior like React-Native itself
* Fix the implementation of request modifier on SDWebImage, which have bugs on 5.8.0 (will fix in 5.8.1), revert the dependency bump
* Revert the changes to bypass SSL error
* Remove the unused Podfile.lock changes

.gitignore

@@ -22,6 +22,10 @@ DerivedData
 *.xcuserstate
 project.xcworkspace
 
+# CocoaPods
+Podfile.lock
+Pods
+
 # Android/IJ
 #
 .idea